Monometallic and bimetallic nanoparticles have been studied as catalysts for alternative energy applications. Metallic nanoparticles are an attractive alternative to bulk metal catalysts because the larger surface area to volume ratio reduces the overall mass of metal used. Furthermore, nano-sized or nano-structured catalysts have been shown to have enhanced catalytic activity when compared to their bulk counterparts, even when activity is normalized to available surface area. Modeling and experimental efforts suggest that reasons for such activity include: size-induced surface strain, an increase in crystal defects that serve as catalytic sites, unique structural compositions of multiple metals, and the occurrence of unique orbital interactions that allow an optimization of the activity of surface sites involved in catalytic and poisoning interactions.
A wide variety of nanoparticle synthesis techniques have been developed. Such techniques have allowed researchers to produce nanoparticles with specific sizes, shapes, and compositions, including multi-metallic nanoparticles with alloy or core-shell configurations.
The majority of successful catalysts for fuel cells contain at least one precious metal, and the most common catalyst material has been platinum. However, recent efforts have begun to focus on the reduction or elimination of precious metals in nano-catalysts due to costs of the precious metals. Nanoparticle synthesis methods that involve solution-based chemistry are of particular interest because of their ease of use, their versatility and manipulability, and their scalability. Accordingly, it would be beneficial to provide core-shell structured nanoparticles which could be utilized in a wide array of applications such as catalysts, and which are free of precious metals. It would also be beneficial to provide core-shell nanoparticle synthesis methods for producing such nanoparticles which involve solution-based chemistry.